The present invention relates to a novel sintered Al alloy of high strength and wear resistance and in particular to a sintered aluminum-silicon based alloy which improves damage and wear resistance and plastic workability and machinability of opposite materials to be worked, and a method for producing the alloy and uses of the alloy.
Hitherto, AC8A and A390 specified in JIS have been produced as wear resistant Al alloys by a melt casting method. However, an Al--Si based alloy high in Si content is difficult to produce by the melt casting method. That is, when the Si content is more than that forms a eutectoid, there are such defects that coarse proeutectic Si crystal is precipitated to cause reduction of strength and besides difficulty in plastic workability and moreover, the opposite materials to be worked may be damaged by the hard and coarse proeutectic Si crystals. Especially, now miniaturization and weight-saving and high-performance of products are desired and so improvements in strength, plastic workability, cutting workability and wear resistance have been required.
Thus, recently, Al--Si--Fe, Al--Si--Mn and Al--Si--Ni based sintered alloys have been developed using powder metallurgy technique. A method for production of these alloy powders comprises melting an alloy of a given composition, making quenched and solidified powders by gas atomization or the like, compacting the powders and then sintering or hot plastic working the compacting to produce the desired alloy. The quenched and solidified powders contain finely divided and uniformly dispersed proeutectic Si crystals and hence obtained is a high Si material higher in strength than those made by conventional melt casting method.
The sintered alloys of Japanese Patent Kokai (Laid-Open) Nos. 64-56806 and 63-183148 produced by a quenched and solidified powder-sintering method have high strength, but are very low in toughness, which is about 0.2-0.98 kg-m/cm.sup.2 in Charpy impact strength. Japanese Patent Kokai No. 60-131944 discloses a mixture of quenched and solidified Al alloy powders and 0.5-10 vol % of carbon powders, in which high strength cannot be obtained.
In Japanese Patent Kokai No. 55-97447, graphite, sulfides and fluorides are added as solid lubricating components and so high strength cannot be expected as in Japanese Patent Kokai No. 60-131944.
Furthermore, Japanese Patent Koaki Nos. 63-183148, 1-159345, 2-61023, 2-61024 and 2-70036 disclose to produce alloys by compacting alloy powders containing 5-40% of Si and Cu, Mg, Mn, Fe, W, Ni, Cr, Co, Ce, Ti, Zr, V, Mo and the like and then subjecting the compacted alloy to hot plastic working, but the resulting alloys do not have a sufficient strength and toughness.
As explained above, the conventional Al--Si--Fe, Al--Si--Mn, and Al--Si--Ni based sintered alloys are high in strength, but low in toughness. Further, the sintered Al alloys containing solid lubricants are also considerably low in strength and toughness. Therefore, they have a limit in use as members to which impact force is repeatedly applied and as sliding wear members used under high loading.